Ring magnet rotor of motor with coating material

ABSTRACT

A rotor of a motor capable of improving durability of the motor by increasing a bonding force between a ring magnet and a resin. The rotor includes a ring magnet having an insertion hole passing through the center thereof, a shaft inserted into the insertion hole, and a resin that is disposed between the insertion hole and the shaft and fixes the ring magnet and the shaft. The resin extends to upper and lower surfaces of the ring magnet so as to cover at least parts of the upper and lower surfaces of the ring magnet.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation Application of prior U.S. patentapplication Ser. No. 14/107,117 filed Dec. 16, 2013, which claimspriority under 35 U.S.C. §119 to Korean Patent Application No.10-2012-0147296 filed on Dec. 17, 2012, the disclosure of which isincorporated herein by reference in its entirety.

BACKGROUND

1. Field

The present application relates to a rotor of a motor and, moreparticularly, to a rotor constituting a ferrite magnet motor.

2. Background

A vehicle transmission is a mechanism that is manually operated byoperation of a clutch by a user or is automatically operated accordingto a speed. The transmission includes a motor.

As the motor of the transmission, an interior permanent magnet (IPM)motor in which a permanent magnet is buried in a rotor is generallyused.

The IPM motor uses a NdFeB permanent magnet that is lightweight and hasvery strong magnetism, and has high efficiency and output density.

The NdFeB permanent magnet contains neodymium that is a rare-earthelement. Due to increases in prices of rare-earth elements, amanufacturing cost of the motor itself is inevitably increased.

For this reason, a recent trend shows that interest is focused on arare-earth-free motor in which no rare-earth elements are used.

Rare-earth-free motors include a ferrite magnet motor, an inductionmotor, a reluctance motor, and so on. Among these motors, the ferritemagnet motor is most representative.

The ferrite magnet motor is a motor using a ferrite magnet that is aceramic magnet. In comparison with the rare-earth motor, the ferritemagnet motor is inexpensive, and is easily designed.

The ferrite magnet motor is generally made up of a ferrite ring magnethaving an insertion hole, and a shaft inserted into the insertion hole.The ring magnet and the shaft are fixed by a resin.

Here, the resin is disposed only on a contact region between the shaftand the ring magnet.

For this reason, the ferrite magnet motor provides a low bonding forcebetween the ring magnet and the resin. When the motor is abruptlystopped, the ring magnet is separated from the resin due to inertia of arotor.

Further, the ferrite magnet is very vulnerable to impact by nature.Since upper and lower surfaces of the ring magnet are exposed to theoutside, cracks are frequently generated when the motor is used.Performance of the motor is reduced by leakage from such cracks.

The above references are incorporated by reference herein whereappropriate for appropriate teachings of additional or alternativedetails, features and/or technical background.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments will be described in detail with reference to thefollowing drawings in which like reference numerals refer to likeelements wherein:

FIG. 1 is a side cross-sectional view showing a rotor of a motoraccording to an embodiment of the present application;

FIG. 2 shows an upper surface of the rotor of the motor according to theembodiment of the present application;

FIG. 3 is a side cross-sectional view showing a rotor of a motoraccording to another embodiment of the present application;

FIG. 4 shows an upper surface of the rotor of the motor according to theother embodiment of the present application;

FIG. 5 is a graph showing results of measuring slip torque of a motor towhich the rotor according to the embodiment of the present applicationis applied;

FIG. 6 is a graph showing results of measuring an effect of Tefloncoating according to the embodiment of the present application; and

FIG. 7 is a conceptual view of the motor according to the embodiment ofthe present application.

DETAILED DESCRIPTION

Hereinafter, exemplary embodiments of the present application will bedescribed in detail. However, the present application can be implementedin various forms, and embodiments thereof are shown by way of example inthe drawings and will herein be described in detail. It should beunderstood, however, that there is no intent to limit exampleembodiments to the particular forms disclosed, but on the contrary,example embodiments are to cover all modifications, equivalents, andalternatives falling within the scope of the application.

Although the terms first, second, etc. may be used to describe variouselements, these elements are not limited by these terms. These terms areonly used to distinguish one element from another. For example, a firstelement could be termed a second element, and, similarly, a secondelement could be termed a first element, without departing from thescope of exemplary embodiments. The term “and/or” includes any and allcombinations of one or more of the associated listed items.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present.

It will also be understood that when a component such as a layer, afilm, a region, or a plate is referred to as being “on” anothercomponent, the component may be “directly on” the other component, orintervening components may be present. In contrast, when a component maybe “directly on” another component, no intervening components may bepresent.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of exemplaryembodiments. The singular forms “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises,”“comprising,” “includes” and/or “including,” when used herein, specifythe presence of stated features, integers, steps, operations, elements,components and/or groups thereof, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components and/or groups thereof.

Unless otherwise defined, all terms used herein, including technical orscientific terms, have the same meanings as those generally understoodby those with ordinary knowledge in the field of art to which theapplication belongs. Such terms as those defined in a generally useddictionary are to be interpreted to have the meanings equal to thecontextual meanings in the relevant field of art, and are not to beinterpreted to have ideal or excessively formal meanings unless clearlydefined in the present application

With reference to the appended drawings, exemplary embodiments of thepresent application will be described in detail below. To aid inunderstanding the present application, like numbers refer to likeelements throughout the description of the figures, and the descriptionof the same elements will be not reiterated.

FIG. 1 is a side cross-sectional view showing a rotor of a motoraccording to an embodiment of the present application, and FIG. 2 showsan upper surface of the rotor.

Referring to FIGS. 1 and 2, a rotor of a motor according to anembodiment of the present application includes a shaft 100, a ringmagnet 200, and a resin 300.

The ring magnet 200 has an insertion hole 201 passing through the centerthereof. The shaft 100 is inserted into the insertion hole 201 of thering magnet 200.

The resin 300 is disposed between an inner surface of the insertion hole201 and the shaft 100, and fixes the ring magnet 200 and the shaft 100.Further, the resin 300 extends to upper and lower surfaces of the ringmagnet 200 so as to cover the upper and lower surfaces of the ringmagnet 200.

In other words, the resin 300 is a fixing member fixing the ring magnet200 and the shaft 100. A pocket 301 in which the ring magnet 200 ishoused is formed in an outer circumferential surface of the resin 300.

In detail, the resin 300 may cover at least parts of the upper and lowersurfaces of the ring magnet 200. That is, the resin 300 may be formed tocover parts of the upper and lower surfaces of the ring magnet 200 asshown in FIGS. 1 and 2, or to cover all of the upper and lower surfacesof the ring magnet 200.

In the rotor of the conventional ferrite magnet motor, the resin isdisposed only between the insertion hole of the ring magnet and theshaft. Thus, unlike the present application shown in FIGS. 1 and 2, therelated art is configured so that the upper and lower surfaces of theresin are flush with the upper and lower surface of the ring magnet.

In the related art, a bonded region between the resin and the ringmagnet is present only on the inner surface of the insertion hole. Assuch, as mentioned in the section “Discussion of Related Art,” thebonding force between the ring magnet and the shaft is consequently low,and the upper and lower surfaces of the ring magnet are exposed to theoutside, causing cracking and leakage.

In contrast, in the present application, the resin 300 is formed tocover the upper and lower surfaces of the ring magnet 200 as shown inFIGS. 1 and 2. As such, a bonded surface between the ring magnet 200 andthe resin 300 is increased compared to the related art, and a mutualbonding force can be improved. Further, due to the resin 300, exposedareas of the upper and lower surfaces of the ring magnet 200 arereduced. As such, cracks generated from the ring magnet 200 are reduced.Even when cracking occurs, leakage to the outside can be prevented, andperformance of the motor can be improved.

According to an embodiment, the resin 300 may be formed by injectionmolding.

FIGS. 3 and 4 show a rotor of a motor according to another embodiment ofthe present application. FIG. 3 is a side cross-sectional view, and FIG.4 shows an upper surface of the rotor.

In the embodiment of FIGS. 1 and 2, the upper and lower surfaces of thering magnet 200 and the inner surface of the insertion hole 201 areformed in a straight line. However, in the embodiment of FIGS. 3 and 4,at least parts of upper and lower surfaces of a ring magnet 200 and aninner surface of an insertion hole 201 are provided with at least onemagnet fixing recess 202. In detail, the magnet fixing recess 202 may beformed in the upper and lower surfaces of the ring magnet 200, andextend to the inner surface of the insertion hole 201. Disposition of ashaft 100, a ring magnet 200, and a resin 300 is identical as in theembodiment of FIGS. 1 and 2.

When the resin 300 is formed in and on the upper and lower surfaces ofthe insertion hole 201 of the ring magnet 200, the resin 300 is insertedinto the magnet fixing recess 202. Thereby, a bonding force between thering magnet 200 and the resin 300 can be further improved.

To be more specific, when a contact surface between the ring magnet 200and the resin 300 is flat, a flat surface of the ring magnet 200 may beseparated from the resin 300 by inertia of the ring magnet 200 in theprocess in which the rotor is rotated and then stopped in view of acharacteristic of the rotor repeating rotation and a stop.

However, when the resin 300 is inserted into the magnet fixing recess202, a sort of fastening structure in which the resin 300 functions tocatch the ring magnet 200 is formed. As such, the bonding force can beimproved.

At least one magnet fixing recess 202 may be locally or continuouslyformed in a bonded surface with the resin 300, and may be formed in astepped shape as shown in FIGS. 3 and 4.

Further, to provide the same function as the fixing recess 202 of thering magnet 200, the shaft 100 is provided with at least one shaftfixing recess 101 in a bonded surface with the resin 300. At least oneshaft fixing recess 101 is locally or continuously formed in an outercircumferential surface of the shaft 100 so as to improve a bondingforce between the resin 300 and the shaft 100.

FIG. 5 is a graph showing results of measuring slip torque of a motor towhich the rotor according to the embodiment of the present applicationis applied. The slip torque refers to torque that causes the magnet toslip apart from the resin when the rotor is abruptly stopped while beingrotated.

In FIG. 5, a longitudinal axis indicates a value of torque (N·m), and atransverse axis indicates a conventional motor for the left (Before) andthe motor using the rotor according to the present application for theright (After).

Referring to FIG. 5, the torque of about 25 N·m is generated in the caseof the conventional motor, and the torque of about 45 N·m is generatedin the case of the motor using the rotor according to the presentapplication. It can be seen that the torque of the motor using the rotoraccording to the present application is remarkably improved compared tothat of the conventional motor.

Meanwhile, in another embodiment of the present application, the ringmagnet 200 may be coated with a coating material. Teflon may be used asthe coating material.

Although the exposed surfaces, i.e. the parts of the upper and lowersurfaces, and the outer circumferential surface of the ring magnet 200are coated with a coating material 400 in the embodiment (FIGS. 1 and 2)and the other embodiment (FIGS. 3 and 4) of the present application,this is merely illustrative. The surface of the ring magnet 200 may becoated in part or in whole.

Further, a coating layer may be formed on the resin 300 extending to theupper and lower surfaces of the ring magnet 200 (an outer surface of thepocket). In this case, the slip torque of the ring magnet 200 can beincreased by a bonding force between the resin 300 and the coatinglayer.

A coating method may include a step of sanding the surface of the ringmagnet 200 to be coated, a step of preheating the coating material 400to coat it on the sanded surface of the ring magnet 200, and a step ofpost-heating the coated coating material 400. This coating method ismerely an example. Without being limited thereto, various coatingmethods may be applied according to a type of the coating material 400.

Here, the coating material 400 may be formed at a thickness of 10 to 30μm. When the thickness of the coating material is less than 10 μm,effects of inhibiting corrosion and preventing cracks cannot beobtained. When the thickness of the coating material is more than 30 μm,magnetism of the ring magnet is excessively shielded.

The coating material formed at a thickness of 10 to 30 μm can protectthe surface of the ring magnet 200 without influencing the magnetism ofthe ring magnet 200, and further improve the effect of preventing thecracks.

In addition, due to the coating, an effect of preventing corrosion ofthe ring magnet 200 can be additionally obtained.

FIG. 6 is a graph showing results of measuring an effect of Tefloncoating according to the embodiment of the present application.

In FIG. 6, a longitudinal axis indicates a value of resisting pressureof the ring magnet 200, and a transverse axis indicates a case in whichthe Teflon coating is not performed (for the left) and a case in whichthe Teflon coating of 20 μm is performed (for the right).

Referring to FIG. 6, it can be seen that the case in which the Tefloncoating is performed is improved in resisting pressure performancecompared to the case in which the Teflon coating is not performed.

The rotor of the motor of the present application as described above canbe applied to a ferrite magnet motor. In addition to the ferrite magnetmotor, the rotor of the present application may be variously applied toany motor, in which a shaft and a magnet are fixed by a resin, asneeded.

Further, the applied range is not limited to the motor for atransmission of a vehicle. The rotor may be applied to any device forwhich a motor is used.

FIG. 7 is a conceptual view of the motor according to the embodiment ofthe present application.

Referring to FIG. 7, the motor includes a housing 800, a stator 500disposed in the housing 800, and a rotor 100, 200, 300 disposed to berotatable relative to the stator 500. The housing 800 has a space inwhich the stator 500 and the rotor 100, 200, 300 are housed. When poweris applied, the shaft 100 is rotated by an electromagnetic interactionbetween the stator 500 and the magnet 200 of the rotor. Opposite ends ofthe shaft 100 are supported by bearings 600 and 700. One side of theshaft is connected to a clutch of the vehicle so as to enable a gearshifting function. The configuration of the rotor is the same as theforegoing, and detailed description thereof is omitted.

The present application is directed to providing a rotor of a motorcapable of improving durability of the motor by increasing a bondingforce between a ring magnet and a resin.

Further, the present application is directed to providing a rotor of amotor capable of reducing cracks generated from a ring magnet.

According to an aspect of the present application, there is provided arotor of a motor, which includes: a ring magnet having an insertion holepassing through the center thereof; a shaft inserted into the insertionhole; and a resin that is disposed between the insertion hole and theshaft and fixes the ring magnet and the shaft. The resin extends toupper and lower surfaces of the ring magnet so as to cover at leastparts of the upper and lower surfaces of the ring magnet.

Here, the ring magnet may include at least one magnet fixing recess thatis formed in the upper or lower surfaces thereof and extend to a bondedsurface with the resin, and the resin may be inserted into the magnetfixing recess.

Further, the shaft may include at least one shaft fixing recess that isformed in a bonded surface with the resin, and the resin may be insertedinto the shaft fixing recess.

Further, the surfaces of the ring magnet may be coated with a coatingmaterial.

Also, at least parts of the upper and lower surfaces and an outercircumferential surface of the ring magnet may be coated with a coatingmaterial.

Further, the coating material may be Teflon.

Further, the coating material may be formed at a thickness of 10 to 30μm.

In addition, the resin may be subjected to injection molding.

According to the present application, the resin is disposed between theinsertion hole of the ring magnet and the shaft, and extends to theupper and lower surfaces of the ring magnet so as to cover at leastparts of the upper and lower surfaces of the ring magnet. Thereby, afixing force of the ring magnet is improved, and durability of the motoris improved.

Further, since the resin covers the upper and lower surfaces of the ringmagnet, an exposed area of the ring magnet is reduced, and generation ofcracks is reduced. Even when the cracks are generated from the ringmagnet, the resin disposed on the upper and lower surfaces of the ringmagnet protects the ring magnet, and thus there is no risk of reducingperformance of the motor due to leakage of debris outside the rotor fromthe cracks.

In addition, the ring magnet is coated, and an effect of preventing thecracks of the ring magnet can be further improved.

Any reference in this specification to “one embodiment,” “anembodiment,” “example embodiment,” etc., means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the application.The appearances of such phrases in various places in the specificationare not necessarily all referring to the same embodiment. Further, whena particular feature, structure, or characteristic is described inconnection with any embodiment, it is submitted that it is within thepurview of one skilled in the art to effect such feature, structure, orcharacteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

What is claimed is:
 1. A rotor of a motor comprising: a shaft; a resincoupled to the shaft; and a ferrite magnet including a through hole andcoupled to the resin, wherein the resin covers an inner circumferentialsurface of ferrite magnet, an upper surface of the ferrite magnet and alower surface of the ferrite magnet, wherein the ferrite magnet includesa plurality of magnet fixing recess which is disposed on the uppersurface of the ferrite magnet and coupled to the resin, wherein themagnet fixing recess includes a bottom surface extending perpendicularlyto the inner circumferential surface of the through hole and a sidesurface connecting the bottom surface and the upper surface of theferrite magnet, wherein the magnet fixing recess widens from the bottomsurface toward the upper surface, wherein the shaft includes a pluralityof shaft fixing recess in a surface in contact with the resin.
 2. Therotor of claim 1, wherein an outer circumference surface of the ferritemagnet is coated with a coating material.
 3. The rotor of claim 2,wherein the coating material includes Teflon and has a thickness of 10μm to 30 μm.
 4. The rotor of claim 1, wherein the resin is formed byinjection molding.
 5. The rotor of claim 1, wherein a distance from anoutermost end of the resin to the center of the shaft is greater than adistance from an outermost end of the magnet fixing recess to the centerof the shaft.
 6. The rotor of claim 1, wherein the magnet fixing recesshas a semicircular shape or a semioval shape.
 7. The rotor of claim 1,wherein a height from the upper surface to the lower surface of theresin is greater than a height of an outer circumferential surface ofthe ferrite magnet.
 8. The rotor of claim 1, wherein the shaft includesa first region between one end of the shaft at the axial center of theshaft and a second region between the other end of the shaft at theaxial center of the shaft, and the ferrite magnet and the resin aredisposed only in the first region.
 9. The rotor of claim 1, wherein theshortest distance from the outer surface of the shaft to the outermostside of the resin is longer than the shortest distance from the outersurface of the shaft to the outermost side of the magnet fixing recessand shorter than the shortest distance from the outer surface of theshaft to the outermost side of the ferrite magnet.
 10. A motorcomprising: a housing; a stator disposed in the housing; and a rotordisposed in the stator, wherein the rotor includes a shaft, a resincoupled to the shaft and a ferrite magnet including a through hole andcoupled to the resin, wherein the resin covers an inner circumferentialsurface of ferrite magnet, an upper surface of the ferrite magnet and alower surface of the ferrite magnet, wherein the ferrite magnet includesa plurality of magnet fixing recess which is disposed on the uppersurface of the ferrite magnet and into which the resin is inserted,wherein the magnet fixing recess includes a bottom surface extendingperpendicularly to the inner circumferential surface of the through holeand a side surface connecting the bottom surface and the upper surface,wherein the magnet fixing recess widens from the bottom surface towardthe upper surface, wherein the shaft includes a plurality of shaftfixing recess in a surface in contact with the resin.